Spider mites are a common garden pest that can quickly damage and even kill plants. These tiny pests are related to spiders and can be very difficult to spot due to their small size. An infestation often goes unnoticed until the damage becomes severe. The good news is there are several effective ways to get rid of spider mites and prevent future infestations.
What are Spider Mites?
Spider mites belong to the mite family Tetranychidae and are classified as a type of arachnid, not an insect. There are over 1,200 identified species of spider mites. They are extremely tiny, often less than 1 mm in size, and can appear as specks of dust on the plant.
Spider mites have oval-shaped bodies with eight legs They come in a variety of colors including red, yellow, green, and brown Some species can change color over their lifecycle.
These tiny pests spin silky webs on plants, similar to spiders They use these webs for protection and laying eggs Spider mite webbing is the most obvious sign of an infestation.
Spider Mite Lifecycle
The spider mite lifecycle has five stages – egg, larva, protonymph, deutonymph, and adult. It takes between 5-20 days to complete one generation.
- Adult females can live for 2-4 weeks and lay up to 20 eggs per day.
- Eggs hatch into larvae within 3-5 days.
- Larvae mature into protonymphs and then deutonymphs before reaching adulthood.
- Hot, dry conditions allow spider mites to breed rapidly with overlapping generations.
How to Identify Spider Mites
Look for Webbing
The most obvious sign of spider mites is the presence of fine, silky webs on plant leaves and stems. Check leaf joints and undersides where mites like to hide. A minor infestation may just have a few strands of webbing.
Check for Specks
Spider mites can be hard to see with the naked eye. Use a magnifying glass to look for tiny dots crawling on the webs and undersides of leaves. Tapping leaves over white paper can dislodge mites for easier viewing.
Look for Damage
Spider mite feeding causes stippling, discolored spots and blotches on leaves. Damaged leaves may turn yellow, bronze or dry up. Leaf drop often occurs in severe infestations.
How to Get Rid of Spider Mites Naturally
Wash Them Off
Blast plants with water to dislodge mites. Use a jet setting on the hose or kitchen/bathroom sink sprayer. Make sure to spray the undersides of leaves.
Apply Insecticidal Soap
Insecticidal soaps containing potassium salts of fatty acids can kill mites through contact. Spray all surfaces of plant leaves for best results.
Use Neem Oil
Neem oil disrupts the spider mite life cycle and eggs. It’s also a repellent. Mix neem oil with water and a bit of mild soap and spray plants.
Rub Alcohol Spray
A spray of 70% isopropyl alcohol directly on mites can kill them by dessication. Test on a few leaves first before treating the whole plant.
Encourage Predators
Release ladybugs, lacewings and predatory mites which feed on spider mites. These biological controls are a natural way to reduce mite populations.
Use Horticultural Oils
Light oils made from soybean, cottonseed or mineral oils smother spider mites when applied as a foliar spray. Be sure to cover undersides of leaves.
How to Prevent Spider Mites
- Quarantine and inspect new plants before bringing home
- Provide proper care and moisture for plants
- Promote air circulation between plants
- Keep garden debris cleaned up
- Hose plants periodically with water
- Release predatory mites early in season
- Avoid excess pesticide use which kills beneficial insects
Frequently Asked Questions
What plants do spider mites attack?
Spider mites feed on a wide variety of plants. Some of the most commonly affected are roses, beans, tomatoes, squash, melons, cole crops, citrus, and many flowering plants. They also frequently attack houseplants.
Where do spider mites come from?
Spider mites can blow in on the wind, travel on plants, pots or gardening tools, or get brought indoors on clothing. A common cause is bringing infested plants home from nurseries.
How do you kill spider mites organically?
Effective organic spider mite treatments include insecticidal soap, neem oil, horticultural oils, rubbing alcohol, and water sprays. Encouraging beneficial predators is also an organic approach.
Are spider mites harmful to humans?
Spider mites do not bite or harm humans. They only feed on plant matter. Their tiny size prevents them from breaking human skin to feed.
What time of year are spider mites most active?
Spider mites thrive in hot, dry conditions above 80°F. Peak activity is usually late summer during July-September. However, they can be a problem indoors year round on houseplants.
Can spider mite damage be reversed?
If caught early before widespread damage, the effects of spider mites can be reversed. Remove heavily infested leaves then treat with miticides. The plant may recover with proper care. But severe, prolonged infestations can permanently damage or kill plants.
Most Affected Plants
Outdoor plants most often affected are cucurbits (squash, pumpkins, cucumbers, etc.), beans, tomatoes, and a wide range of landscape trees and shrubs. Many indoor houseplants can be affected by spider mites, especially those with thin, tender leaves. You are most likely to see spider mite damage in warm, dry conditions.
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Use Insecticidal Soaps or Oils
Insecticidal soaps that are formulated to kill insects and other pests are often quite effective against spider mites. Treatment will need to be repeated frequently until the mite problem is under control.
Horticultural oil products made from highly refined plant oils, such as citrus, are also very effective against mites since they smother the pests. Horticultural oils are less likely than chemical pesticides to kill beneficial insects.